diff --git a/mirage/route-handlers/crates.js b/mirage/route-handlers/crates.js
index f189568ddad..fcbe824e23f 100644
--- a/mirage/route-handlers/crates.js
+++ b/mirage/route-handlers/crates.js
@@ -265,6 +265,11 @@ export function register(server) {
   });
 
   server.delete('/api/v1/crates/:name/:version/yank', (schema, request) => {
+    let { user } = getSession(schema);
+    if (!user) {
+      return new Response(403, {}, { errors: [{ detail: 'must be logged in to perform that action' }] });
+    }
+
     const { name, version: versionNum } = request.params;
     const crate = schema.crates.findBy({ name });
     if (!crate) {
@@ -276,10 +281,17 @@ export function register(server) {
       return notFound();
     }
 
-    return {};
+    version.update({ yanked: true });
+
+    return { ok: true };
   });
 
   server.put('/api/v1/crates/:name/:version/unyank', (schema, request) => {
+    let { user } = getSession(schema);
+    if (!user) {
+      return new Response(403, {}, { errors: [{ detail: 'must be logged in to perform that action' }] });
+    }
+
     const { name, version: versionNum } = request.params;
     const crate = schema.crates.findBy({ name });
     if (!crate) {
@@ -291,7 +303,9 @@ export function register(server) {
       return notFound();
     }
 
-    return {};
+    version.update({ yanked: false });
+
+    return { ok: true };
   });
 
   server.get('/api/v1/crates/:name/:version/readme', (schema, request) => {
diff --git a/tests/mirage/crates/versions/yank/unyank-test.js b/tests/mirage/crates/versions/yank/unyank-test.js
new file mode 100644
index 00000000000..bf5607e9191
--- /dev/null
+++ b/tests/mirage/crates/versions/yank/unyank-test.js
@@ -0,0 +1,55 @@
+import { module, test } from 'qunit';
+
+import fetch from 'fetch';
+
+import { setupTest } from '../../../../helpers';
+import setupMirage from '../../../../helpers/setup-mirage';
+
+module('Mirage | PUT /api/v1/crates/:crateId/unyank', function (hooks) {
+  setupTest(hooks);
+  setupMirage(hooks);
+
+  test('returns 403 if unauthenticated', async function (assert) {
+    let response = await fetch('/api/v1/crates/foo/1.0.0/unyank', { method: 'PUT' });
+    assert.strictEqual(response.status, 403);
+    assert.deepEqual(await response.json(), {
+      errors: [{ detail: 'must be logged in to perform that action' }],
+    });
+  });
+
+  test('returns 404 for unknown crates', async function (assert) {
+    let user = this.server.create('user');
+    this.authenticateAs(user);
+
+    let response = await fetch('/api/v1/crates/foo/1.0.0/unyank', { method: 'PUT' });
+    assert.strictEqual(response.status, 404);
+    assert.deepEqual(await response.json(), { errors: [{ detail: 'Not Found' }] });
+  });
+
+  test('returns 404 for unknown versions', async function (assert) {
+    this.server.create('crate', { name: 'foo' });
+
+    let user = this.server.create('user');
+    this.authenticateAs(user);
+
+    let response = await fetch('/api/v1/crates/foo/1.0.0/unyank', { method: 'PUT' });
+    assert.strictEqual(response.status, 404);
+    assert.deepEqual(await response.json(), { errors: [{ detail: 'Not Found' }] });
+  });
+
+  test('unyanks the version', async function (assert) {
+    let crate = this.server.create('crate', { name: 'foo' });
+    let version = this.server.create('version', { crate, num: '1.0.0', yanked: true });
+    assert.true(version.yanked);
+
+    let user = this.server.create('user');
+    this.authenticateAs(user);
+
+    let response = await fetch('/api/v1/crates/foo/1.0.0/unyank', { method: 'PUT' });
+    assert.strictEqual(response.status, 200);
+    assert.deepEqual(await response.json(), { ok: true });
+
+    user.reload();
+    assert.false(version.yanked);
+  });
+});
diff --git a/tests/mirage/crates/versions/yank/yank-test.js b/tests/mirage/crates/versions/yank/yank-test.js
new file mode 100644
index 00000000000..8dc79b03691
--- /dev/null
+++ b/tests/mirage/crates/versions/yank/yank-test.js
@@ -0,0 +1,55 @@
+import { module, test } from 'qunit';
+
+import fetch from 'fetch';
+
+import { setupTest } from '../../../../helpers';
+import setupMirage from '../../../../helpers/setup-mirage';
+
+module('Mirage | DELETE /api/v1/crates/:crateId/yank', function (hooks) {
+  setupTest(hooks);
+  setupMirage(hooks);
+
+  test('returns 403 if unauthenticated', async function (assert) {
+    let response = await fetch('/api/v1/crates/foo/1.0.0/yank', { method: 'DELETE' });
+    assert.strictEqual(response.status, 403);
+    assert.deepEqual(await response.json(), {
+      errors: [{ detail: 'must be logged in to perform that action' }],
+    });
+  });
+
+  test('returns 404 for unknown crates', async function (assert) {
+    let user = this.server.create('user');
+    this.authenticateAs(user);
+
+    let response = await fetch('/api/v1/crates/foo/1.0.0/yank', { method: 'DELETE' });
+    assert.strictEqual(response.status, 404);
+    assert.deepEqual(await response.json(), { errors: [{ detail: 'Not Found' }] });
+  });
+
+  test('returns 404 for unknown versions', async function (assert) {
+    this.server.create('crate', { name: 'foo' });
+
+    let user = this.server.create('user');
+    this.authenticateAs(user);
+
+    let response = await fetch('/api/v1/crates/foo/1.0.0/yank', { method: 'DELETE' });
+    assert.strictEqual(response.status, 404);
+    assert.deepEqual(await response.json(), { errors: [{ detail: 'Not Found' }] });
+  });
+
+  test('yanks the version', async function (assert) {
+    let crate = this.server.create('crate', { name: 'foo' });
+    let version = this.server.create('version', { crate, num: '1.0.0', yanked: false });
+    assert.false(version.yanked);
+
+    let user = this.server.create('user');
+    this.authenticateAs(user);
+
+    let response = await fetch('/api/v1/crates/foo/1.0.0/yank', { method: 'DELETE' });
+    assert.strictEqual(response.status, 200);
+    assert.deepEqual(await response.json(), { ok: true });
+
+    user.reload();
+    assert.true(version.yanked);
+  });
+});